Following injury, the inherent regenerative response of skeletal muscle depends on an activated microenvironment consisting of muscle progenitor cells and a heterogeneous macrophage phenotype. These microenvironmental factors can be negatively impacted through musculoskeletal disease, volumetric muscle loss (VML), and the decreased regenerative capacity of stem cells and immunosenesence associated with advanced age. Biologic scaffolds composed of extracellular matrix (ECM) have been used to promote the constructive remodeling of defects in a variety of soft tissues. These surgically placed scaffolds are composed of growth factors and matricryptic peptides which are able to positively impact the skeletal muscle microenvironment by recruiting progenitor cells and promoting an M1 to M2 macrophage phenotypic transition. Furthermore, ECM scaffolds have been used to effectively augment the skeletal muscle response to VML. The current proposal seeks to examine the ability of ECM scaffolds to mitigate age-related changes to the skeletal muscle microenvironment through increased myogenic progenitor cell recruitment and modulation of macrophage phenotype.